So-called vectoring or vectored data transmission is a technique for coordinated transmission or reception of data from a plurality of transmitters to a plurality of receivers via a plurality of transmission channels in order to improve the transmission, for example to reduce the influence of crosstalk. Either transmitters or receivers are co-located. Vectoring is sometimes also referred to as Spectrum Management Level 3.
For example, in DSL (digital subscriber line) transmission systems, for example VDSL (very high bit rate DSL) transmission systems, data may be transmitted from a central office (CO) or other provider equipment to a plurality of receivers located in different locations, for example in customer premises (CPE), via a plurality of communication lines. Crosstalk resulting from signals on different lines transmitted in the same direction, also referred to as far end crosstalk (FEXT), may result in a reduced data throughput. Through vectoring, signals transmitted over the plurality of communication lines from the central office or received via the plurality of communication lines in the central office may be processed jointly in order to reduce such crosstalk, which joint processing corresponds to the above-mentioned vectoring. In this respect, the reduction of crosstalk by coordinated transmission of signals is sometimes referred to as crosstalk precompensation, whereas the reduction of crosstalk through joint processing of the received signals is sometimes referred to as crosstalk cancellation. The communication lines which are processed jointly are sometimes referred to as vectored group.
For this kind of crosstalk reduction, for example in an initialization phase of the data transmission system or during operation of the data transmission system, parameter describing the crosstalk between the communication connections are obtained and the crosstalk reduction is performed based on these parameters.
The computational effort of this crosstalk reduction increases with increasing number of transmission channels, for example communication lines, involved. Therefore, in transmission systems involving a large number of transmission channels, sometimes so-called partial vectoring is used, where only a part of the transmission channels are subjected to vectoring. In this case, a selection has to be made which transmission channels or which crosstalk paths add to the vectored group.
Another possible approach to reduce crosstalk in communication systems is so-called spectrum balancing, also sometimes referred to as Spectrum Management Level 2. In this approach, transmission powers for the individual transmission channels are controlled to reduce the effect of crosstalk at least for some transmission channels.